Automatic film jam shutoff



Oct. 21, 1941. SHORR 2,259,493

AUTOMATIC FILM JAM HUTOFF Filed Apri l 4, 1941 v 46 Z TIE 1 M54 1///\/ 6/ 02? M W 5 M Jr ole/ways Patented Oct. 21, 1941 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 5 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to improvements in devices which include means for moving a tape or strip, and particularly to means for controlling the movement of the strip through the apparatus.

In devices of this character, the strip is usually taken from a supply reel by a feed device which, after performance of its function, ejects it for rewinding on a second reel.

Because of the fact that a rewind reel, when substantially full of tape or strip material, must fewer revolutions in taking up a given length of strip than one that is almost empty, it is a requisite that some provision be made to constantly lower the rotative speed of the rewind reel with respect to that of the feed wheel the rewind reel fills up.

In order to make such compensating devices as simple as possible, it is a custom, known in the art, to make the relative rotations between the feed wheel and the rewind reel in correct proportion for an empty reel, then frictionally drive the rewind reel in order that some slippage in the rewind drive may occur when the strip between the feed and the rewind tautens from the too rapid rotation of the rewinder for the then filled condition of the reel.

Usually the strip employed in a device of this character is more or less fragile, and it follows that the friction of the rewind drive should be very light, yet if it is made sensitive enough to slip from a tautening of the strip Without injury 1 thereto, it may at times slip from other causes, such for instance as lack of lubrication of the rewind reel bearings or excess lubrication on the friction elements, or again, a toofull reel may rub the strip against the reel frame and cause rotation of the reel to cease and when any such abnormal condition exists the strip may continue to be fed from the feed sprocket while the device lacks capacity to take it up and place it on the rewind reel, in which case the excess strip is usually caught by some moving part and damaged or destroyed.

Furthermore, in a device of this character the drive between the power source and the feed wheel is usually of high speed reducing and consequent torque multiplying capacity and when the driven end of such a mechanism becomes jammed and stalled, it not infrequently happens that some of the interconnecting gearing is broken,

Various mechanisms have been proposed to correct the foregoing shortcomings, but in general they comprise means for sensing a deviation of the strip from its proper operative course by maintaining constant contact therewith while it is in motion, with the result that unnecessary wear of the strip itself may occur.

Again in devices which have heretofore been proposed, the trouble sensing means which maintains constant contact with the strip puts it under an initial tension, there being means whereby an increase in the tension will operate the device to arrest rotation of the feed. It follows that where the rewind reel is frictionally driven an increase in the friction of the drive is required, and as heretofore stated the friction of this rewind drive is preferably kept as low as possible.

It is therefore, an object of this invention to so construct and arrange the several parts of an embodiment thereof, that the part of the strip which leaves its normal course of travel to operate a means which automatically causes a cessation in strip movement, is placed in compression rather than tension, and thereby assists rather than opposes the friction means of the rewind drive.

Another object of the invention is to provide means located proximate the strip but which is out of contact therewith so long as it is in its normal course of travel, and which is sensitive to a deviation of the strip from its normal course to automatically discontinue power application to the feed mechanism and the rewind reel.

It is another object to provide means, operative when application of power has been thus automatically discontinued, to indicate, by an appropriate signal to the attendant that this has occurred.

It is still another object to so construct and arrange the device, which is contacted and operated by the strip in deviating from its normal course, that it will be extremely sensitive and become fully operative by the light pressure which the strip is capable of exerting.

Other advantages and meritorious features will become evident upon further description, reference being had to the drawing wherein,

Fig. 1 is a longitudinal cross section through an electric switch of known design and especially applicable to the invention.

Fig. 2 is a detail of a part of the switch Fig. 1.

Fig. 3 is another detail of a part of the switch Fig. 1.

Fig. 4 is a side elevation of the complete mechanism, and

Fig. 5 is a wiring diagram of the electric circuits.

It should be understood that the several views of the drawing are more or less schematic and do not necessarily represent the most approved proportion or configuration of the several parts of the structure.

The snap switch of Fig. 1 is substantially that shown in Patent No. 1,950,020 issued May 22, 1934, being a single pole double. throw micro switch of the buckle type. It is selected for the purpose of this invention because of the slight amount of force required to cause its operation. It comprises a casing I!) with cover l2 within which the operative mechanism is contained. Both casing and cover are preferably made of molded plastic insulation.

in electrical communication with a binding post (see Fig. 5).

At the other end, a pad 22 shown in detail plan view Fig. 2, is laid in the bottom of the casing, and the switch blade 24, shown in detail plan View Fig. 3 is laid on the pad, then both are secured in place by the single binding post 26 (see Fig. 5').

The switch blade 24 comprises integrally a widened end 28 to which the contact head 33 (see Fig. 1) is secured, and two spring portions 32, bent in S curve contour as at 34. The ends 36 of the spring portions 32 rest in grooves 38 in the ends of the pad 22, the portions 32 being of such length as to put the 8 portions 34 under slight stress.

A pin 40, slidable in a boss in the cover I2 is provided for applying downward pressure on the blade 24- near its point of support, whereby when the blade 24 is being pressed downwardly by the pin, the stress in the S bent portions will increase until the blade reaches the level of the grooves 38, whereupon an over center condition will take place, the 8 portions thereafter expanding to snap the contact head over to the blade it, thereby electrically connecting post 26 to post 23 whereas it is normally connected to post i8.

A flexible operating blade 42 is riveted at 44 to the cover l2 near the pin 40, the free end 46 having secured thereto the loop catcher 43 the purpose of which will later appear. The switch just described may be broadly designated by the numeral 45.

In the schematic illustration Fig. 4, a feed wheel 50 is rotatably driven by an electric motor 52 through a speed reducing gear box 54, a shaft 55, and gearing 55. The gear box 54 may, Where the nature of the use. to which the device is being put requires an intermittent drive, contain the necessary mechanism for this purpose.

The strip 58 is drawn by the feed wheel 50 from a supply reel 60, passing under guide rollers 62, 64, B5 and 68 and thence to the rewind reel "at. The rewind reel 10 is driven by a spring wire coil belt 12, which is in turn driven by a pulley 14 on the shaft 55', the pulley diameter being so selected that the portion of the strip 58 between the guide roller 68 and the rewind reel "E0 is always in very slight tension, and the belt tension being of such degree as to slip when the strip tension, and the resulting rotational resistance of the rewind reel 10, exceeds a preselected value. a

The location of the switch 45 with respect to the feed wheel 50 is such that the loop catcher 48 is near, but does not ordinarily touch the strip 58, but if for any reason the rotational resistance of reel 10 and the consequent slippage of belt 12 is extensive enough to throw out a loop as shown by the dotted line 78, the loop will nest in the catcher 4S and move it sufliciently to actuate the switch. It should be noted that the portion of strip which forms the loop 16 is in compression, not tension, and that switch actuation does not add to the burden of the belt 1?. but rather lessens it.

In the wiring diagram Fig. 5, the switch 45 is shown bottom toward the observer, with the common terminal 26 connected to one side E8 of a power supply by a conductor 88, the normally operative terminal I8 being connected to one motor terminal 82 by a conductor 8 and the other switch terminal 20 being connected to one side 86 of a signal light 88 by a conductor 90.

The other terminal 932 of the motor is connected by a conductor 94 to the other side 95 of the power supply while the other terminal 93 of the signal 88 makes connection to the power supply through the conductor Hit.

In considering the operation of the device it should be kept in mind that the tension of the belt 72 is preferably very light and the coefficient of friction between it and the pulley Hi very low, so that the capacity of the rewind drive to transmit power is very small, for if it were not so, the portion of the strip 58 between the guide roller 68 and the reel 19 would at times be under unnecessary tension.

When belt 72, therefore, slips abnormally from insufiicient lubrication in the bearings of reel it, or from excess oil on the belt itself, or from any other cause, the loop 16 will jam and nest in the loop catcher 48, operate the switch 45 to disconnect the power supply from the motor 52 and connect it to the signal 88, this notifying the attendant that his attention is required.

In the absence of a device of this character, the

loop 76 continues to increase until it is usually caught between the feed wheel 5d and guide roller 62, after which further rotation of the feed wheel not only destroys the strip but stalls the motor and often breaks some part of the gearing.

While a single embodiment only of the invention is disclosed, and illustrated more or less schematically, it will be obvious that changes in the detail structure, such for instance as in the switch, or in the several drives, may well be made without transcending the scope of the invention as defined in the appended claims.

I claim:

1. A strip winding device comprising a supply reel, a feed wheel, a rewind reel, an electric power source, and an electric motor for driving said feed wheel and said rewind reel, in combination with strip guiding means situated between the feed wheel and the rewind reel adapted, when said rewind reel fails to keep the strip taut by too slow rotation, to define a loop in said strip, a loop catcher outside the loop at the closed end, adapted to be. moved by pressure from said closed end as said' loop becomes longer, an electric switch operable from its normal position to a second position'by movement of said catcher, an electric "signal, and electrically. conductive means operatively'connectin g said motor to said power source through said switch, when said switch is in its normal position, and operativel-y connecting said signal to the power source through said switch when said switch is in its second position.

2. Strip winding mechanism of the character which comprises a supply reel, a feed wheel, a rewind reel, an electric power source, an electric motor, a high reduction gear drive between the motor and the feed Wheel, and a friction drive between the motor and the rewind reel, in combination with means between the feed wheel and the rewind reel for defining a loop in the strip when the friction drive fails to keep the strip taut, a loop catcher outside the closed end of the loop, adapted to be moved by said closed end as said loop lengthens, an electric signal, a two pole electric switch normally connecting the motor to a power source, but adapted to be moved by said catcher to disconnect said motor and connect said signal to said power source.

3. The combination with a strip rewinding mechanism which includes a gear driven feed wheel, a friction driven rewind reel, and an electric motor for driving said feed wheel and rewind reel through the gear drive and friction drive respectively, of a signal, a micro switch near the strip between the feed wheel and the rewind reel, means including spaced apart guides for defining a loop in the strip between the feed wheel and the rewind reel when said friction drive fails, a catcher associated with said switch for receiving the closed end of the loop and adapted to be moved thereby to actuate said switch as said loop lengthens, and conductors for connecting the motor to a power source through said switch when it is in its inoperative position, and to said signal when it has been actuated by said catcher.

4. The combination of a strip winder of that class which includes a feed wheel, a rewind reel and an electric motor for driving said wheel and reel, with guide means for said strip between said wheel and reel, adapted to define a loop in said strip when said reel rotates too slowly, an electrically operative device adjacent said strip where said loop forms, a signal device, and conductive means normally connecting said motor to a power source through said electrically operative device, but adapted by pressure from the closed end of the loop as it lengthens to connect said signal to the said power source.

5. The combination of a strip winder which includes a feed wheel, a rewind reel and power means for rotating said wheel and reel, with guide means for said strip between said wheel and reel adapted, upon a reduction in the speed of said reel relative to said wheel, to define a loop in the strip, a control means proximate said strip where said loop forms, adapted to receive pressure from the bottom of said loop to actuate said control means from a normal to a second position, a signal, and an energy source connectible by said control means when in its normal position to operate the power means to thereby rotate said wheel and reel and when in its second position to operate said signal.

MELVIN SHORR. 

